生物工程专业英语四

1、Lesson FourFoundations of Genetics（遗传学的建立）Allele:等位基因Alternative forms of a gene for a particular characteristic (e.g. attached earlobe(耳垂) genes and free earlobe genes are alternative alleles for ear shape)nonallelic genes:非等位基因非等位基因dihybrid cross: 双因子杂种杂交 AaBb*AaBbtest cross：测交 F1*aa 确定F1是纯合子还是杂合子

2、A cross between a heterozygote(异质结合体) of unknown genotype and an individual homozygous(同型的) for the recessive genes in question.Dominant:显性的 dominance The member of a pair of alleles that shows its effect in the phenotype whatever other allele is present.recessive:隐性的 recessiveness The member of a p

3、air of alleles that does not shows its effect in the presence of any other allelic partner.Genotype:基因型The catalog of genes of an organism, whether or not these genes are expressed.Karyotype:核型，染色体组型phenotype:表现型The physical, chemical, and psychological (心理的)expression of genes possessed by an organ

4、ism.Germ(种子,胚) plasm theory:种质学说A substance thought to be transmitted in the gametes 配子(germ cells) in an unchanged form from generation to generation. The germ plasm was believed to be unaffected by the environment and to give rise to the body cells.Homozygous:纯合的A diploid organism that has two ide

5、ntical alleles for particular characteristic.heterozygous:杂合的A diploid organism that has two different allelic forms of a particular gene. Incomplete dominance:不完全显性The condition in which two allelic genes have a different effect when they are together as a heterozygote in a diploid cell than either

6、 of them have in the homozygous state.Codominance:共显性杂合体中一对等位基因的作用都表现Law of independent assortment:独立分配定律Members of one gene pair will separate from each other independently of the members of other gene pairs.Law of segregation:分离定律 When gametes are formed by a diploid organism, the alleles that con

7、trol a trait(特征) separate from one another into different gametes, retaining their individuality(个性,个体状态)Nondisjunction:不分离不分离The failure of separation of paired chromosomes at metaphase, resulting in one daughter receiving both and the other daughter cell none of the chromosomes in question. Nondis

8、junction can occur during a meiotic or mitotic division.Pangenesis:泛生论，泛生说The theory of heredity postulating(假设) that germs, humours(体液), or essences migrate from individual body cells to the sex organs and contribute to the gametes.Punnett square:庞纳特方格A method used to determine the probabilities of

9、 combination in a zygote(受精卵) Text1. Early theories of inheritanceearly ideas of inheritance included Hippocrates theory of pangenesis and August Weismanns germ plasm theory. 遗传学的早期理论包括Hippocrates的泛生说和A.Weismann的种质学说。 希波克拉底希波克拉底(希腊文希腊文? 英文英文Hippocrates of Cos II 或者 Hippokrates of Kos，约前，约前460前前377)被

10、西方尊为被西方尊为“医学之父医学之父”的古的古希腊希腊著名医生，著名医生，欧洲欧洲医学奠基人，古希医学奠基人，古希腊医师，腊医师，西方西方医学奠基人。提出医学奠基人。提出“体液体液(humours)学说学说”，认为人体由血，认为人体由血液液(blood)、粘液、粘液(phlegm)、黄胆黄胆(yellow bile)和黑胆和黑胆(black bile)四种体液四种体液组成，这四种体液的不同配合使人们有不同的体质。他把疾病看作是发展组成，这四种体液的不同配合使人们有不同的体质。他把疾病看作是发展着的现象，认为医师所应医治的不仅是病而是病人；从而改变了当时医学着的现象，认为医师所应医治的不仅是病而

11、是病人；从而改变了当时医学中以巫术和宗教为根据的观念。主张在治疗上注意病人的个性特征、环境中以巫术和宗教为根据的观念。主张在治疗上注意病人的个性特征、环境因素和生活方式对患病的影响。重视卫生饮食疗法，但也不忽视药物治疗，因素和生活方式对患病的影响。重视卫生饮食疗法，但也不忽视药物治疗，尤其注意对症治疗和预后。他对骨骼、关节、肌肉等都很有研究。他的医尤其注意对症治疗和预后。他对骨骼、关节、肌肉等都很有研究。他的医学观点对以后西方医学的发展有巨大影响。学观点对以后西方医学的发展有巨大影响。August Weismann，(18341914)德国动物学家德国动物学家 。1834 年年1月月17日生于

12、法兰克福日生于法兰克福 ，1914年年11月月5日日卒于弗赖堡卒于弗赖堡 。1856年入格丁根大学学医年入格丁根大学学医 。先后在巴登和奥地利当过。先后在巴登和奥地利当过军医和私人开业医生。军医和私人开业医生。1861年在吉森大学从师于德国动物学家年在吉森大学从师于德国动物学家K.G.洛洛伊卡尔特，学习动物发生学及形态学，伊卡尔特，学习动物发生学及形态学，1863年完成了关于双翅目昆虫年完成了关于双翅目昆虫变态的论文。变态的论文。1866年担任弗赖堡大学医学系动物学和比较解剖学副教年担任弗赖堡大学医学系动物学和比较解剖学副教授，授，1868年在该校创办动物研究所，任第一任所长，年在该校创办动物

13、研究所，任第一任所长，1871年升任教授。年升任教授。60年代中期以后因眼疾不得不终止显微镜下的研究而转向遗传、发生年代中期以后因眼疾不得不终止显微镜下的研究而转向遗传、发生和进化问题的理论探讨。他讲授达尔文进化论多年和进化问题的理论探讨。他讲授达尔文进化论多年 ，直至，直至1912年退休。年退休。Based on experiments with mice, Weismann proposed that hereditary information in gametes transmitted traits to progeny.基于小鼠实验，维丝曼提出遗传信息储存在配子中并将遗传信息传递给

14、后代。 Both of these views incorporated the blending theory: they held that heritable traits of the two parents blend, so that the distinct characteristics of each are lost in offspring.这两个早期观点合起来形成融合理论：子代拥有父母本混合的遗传特征，而不完全象亲代。2. Gregor Mendel and the birth of GeneticsGregor Mendel, an Augustinian monk

15、in the monastery at Brunn, Austria, is known as the “father of genetics”.孟德尔（公元1822公元1884 ），一名奥地利修道士，众所周知的遗传学之父.Having been exposed to theories of the particulate nature of matter while a university student and having a background in mathematics, Mendel carried out a series of carefully planned expe

16、riments that demonstrated the particulate nature of heredity. 当他还是大学生时就提出了物质的粒子属性理论，同时他学习数学。孟德尔进行了一系列周密安排的实验来证实遗传的颗粒性。His revolutionary ideas were neither understood nor accepted until many years after Mendel died.直到他去世后，他的创新性理论才被理解和接受。 孟德尔于孟德尔于1822年出生在海因珍多弗镇，年出生在海因珍多弗镇，1843年他进入奥地利布鲁年他进入奥地利布鲁恩一家奥古斯都

17、修道院。恩一家奥古斯都修道院。1847年他被任命为牧师。从年他被任命为牧师。从1851年到年到1853年年在维也纳大学学习数学和自然科学。从在维也纳大学学习数学和自然科学。从1854年到年到1868年在布鲁恩现代学年在布鲁恩现代学校担任自然科学代课教师。校担任自然科学代课教师。与此同时，孟德尔从与此同时，孟德尔从1856年起开始进行他的著名的植物育种实验。年起开始进行他的著名的植物育种实验。1865年他推导出了著名的遗传学定律，他将定律用一篇论文表述出来，年他推导出了著名的遗传学定律，他将定律用一篇论文表述出来，并将论文呈交给布鲁恩自然历史学会。并将论文呈交给布鲁恩自然历史学会。1866年他的

18、成果被发表在该学会年他的成果被发表在该学会学报上，题目是学报上，题目是“植物杂交实验植物杂交实验”。三年后又在同一杂志上发表了第二。三年后又在同一杂志上发表了第二篇论文。篇论文。1868年孟德尔被任命为牧师会会长，专职行政事务。年孟德尔被任命为牧师会会长，专职行政事务。1900年，孟德尔的研究成果被发现。年，孟德尔的研究成果被发现。3.Mendels classic experimentsMendel studied genetics through plant-breeding experiments with the garden pea, a plant species that is

19、self-fertilizing(自受精) and breeds true(each offspring is identical to the parent in the trait of interest).孟德尔通过豌豆实验研究遗传学，豌豆是自花授粉植物和纯品系。Breed true(to type):生出后代酷似其双亲breed in and in: 近亲交配繁殖breed out and out: (动物的)异种繁殖breed out:在人工繁殖过程中消除(品种的特性)breed up:养育，教育，养成To test the blending theory, he focused h

20、is research on seven distinct characters. Each of these characters, such as seed color and plant height, present only two, clear-cut possibilities.为验证融合理论，他的研究主要集中在7个明显特征上。例如，种子颜色，植株高度，这些特征只有两个明确的可能性。 He also recorded the type and number of all progeny produced from each pair of parent pea plants, a

21、nd followed the results of each cross for two generations.他记录了每一对父母本豌豆产生的所有子代类型和数量，以及再杂交产生子2代的结果。For each of the characters he studied, Mendel found that one trait was dominant while the other was recessive. In the second filial子女的(F2) generation, the ratio of dominant to recessive was 3:1.孟德尔发现对于每个

22、特征而言，要么显性，要么隐性。在F2代中显性与隐性比为3 1。Mendel deduced that this result was possible only if each individual possesses only two hereditary units, one from each parent. The units Mendel hypothesized are today known as alleles, alternative forms of genes.孟德尔推论只有在每个个体仅拥有两个研究遗传单元，并且每个单元来自一个亲代时，实验结果才成立。此遗传单元就是今天共

23、识的等位基因。Genes are the basic units of heredity. An organism that inherits identical alleles for a trait from each parent is said to be homozygous for that trait; if different alleles for a trait are inherited, the organism is heterozygous for that trait.基因是遗传的基本单元，两个一样的等位基因决定一个特征，称纯合;相反，称杂合。When an or

24、ganism is heterozygous for a trait, the resulting phenotype for that trait expresses only the dominant allele.当生物是杂合时，它的表型由显性基因决定。 Thus, the organisms phenotype its physical appearance and properties differs from its genotype, which may include both a dominant and a recessive allele.因此，生物的表型(物理外表和属性

25、)与基因型是不同的，其可同时含有一个显性基因和一个隐性基因。A pictorial(形象化的生动的) representation表现 of all possible combinations of a genetic cross is known as a Punnett square.庞纳特方格可以陈列所有可能的遗传组合。The results of Mendels experiments on dominant and recessive inheritance led to Mendel s first law: the law of segregation. 孟德尔关于显性和隐性遗传

26、的实验结果导致了孟德尔第一定律-分离定律的产生。This law states that for a given trait an organism inherits one allele from each parent.这个定律说的是生物只遗传父母本等位基因对的一个等位基因。 Together these alleles form the allele pair. When gametes are formed during meiosis, the two alleles become separated(halving of chromosome number).这些基因一起形成基因对

27、。减数分裂期形成配子时两个等位基因分离。To gain evidence for his theory Mendel performed test crosses, mating(使配对、使交配) plants of unknown genotype to plants that were homozygous recessive for the trait of interest.为验证此理论，他做了测交实验，即基因型未知的植物与纯合的隐性基因植物杂交。 The ratio of dominant phenotype(if any) in the progeny makes clear wh

28、ether the unknown genotype is heterozygous, homozygous dominant, or homozygous recessive.通过子代中显性表型的比率可以明确测得未知基因型是杂合的或纯合显性的或者纯隐性的。4. Mendels ideas and the law of independent assortmentMendel also performed dihybrid cross, which enabled him to consider how traits are inherited relative to one another.

29、孟德尔还进行了双因子杂合子杂交试验，这个实验使他仔细考虑两个特征是如何相互影响遗传的。This work led to the law of independent assortment, which states that the alleles of genes governing different characters are inherited independently.试验结果产生独立分配定律，即控制不同特征的等位基因独立遗传。An apparent exception to Mendels laws is incomplete dominance, a phenomenon i

30、n which offspring of a cross exhibit a phenotype that is intermediate中间的 between those of the parents.特例是不完全显性。子代的表型是父母本的中间类型。vHowever, incomplete dominance reflects the fact that both alleles for the trait in question exert an effect on the phenotype. The alleles themselves remain separate.v不完全显性说明了两个等位基因对表现都有影响。等位基因会继续分离。Mendel presented his ideas in 1866 in a scientific paper published by the Brunn Society for Natural History. 1866年，孟德尔在由布鲁恩自然历史学会出版的期刊上发表了他的科学论文，陈诉了他的观点。Unfortunately, the meaning of his resear